<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <script src = "./jquery.min.js"></script>
    <style>
        div{
            height: 400px;
            width:600px;
            background-color: pink;
        }

        .current{
            height:200px;
            width: 300px;
        }

        .toggle{
            height: 200px;
            width: 300px;
            background-color: skyblue;
        }
    </style>
</head>
<body>
    <div>演示内容</div>
    <button class = "addstyle">添加样式</button>
    <button class = "removestyle">移除样式</button>
    <button class = "togglestyle">切换样式</button>

    <script>
        $(function(){
            $(".addstyle").click(function(){
                $("div").addClass("current");
            })

            $(".removestyle").click(function(){
                $("div").removeClass("current");
            })

            $(".togglestyle").click(function(){
                $("div").toggleClass("toggle");
            })
        })
    </script>
</body>
</html>